Adjustable safety helmet



FIG. 1 is a top, front and right-side perspective view of an adjustable safety helmet showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof;

FIG. 8 is a rear view thereof in an open position;

FIG. 9 is a bottom plan view thereof in an open position; and,

FIG. 10 is a top plan view thereof in an open position.

The details shown in broken lines form no part of the claimed design. 

CLAIM The ornamental design for an adjustable safety helmet, as shown and described. 